Computer-assisted surgery as indication of choice: total knee arthroplasty in case of retained hardware or extra-articular deformity

Abstract

Purpose: The use of traditional cutting guides during knee arthroplasty in some cases could be extremely difficult, if not impossible, because of angular deformities, IM sclerosis, long-stemmed hip implants, or hardware within the femoral canal that cannot be removed. In these difficult cases navigation-assisted knee arthroplasty should be considered as an effective and appealing option.

Methods: We present 14 cases in which ideal mechanical and prosthetic alignment was achieved with different image-free, computer-assisted navigation systems, because of an extra-articular deformity (group A, nine patients) or because of a retained implant or hardware (group B, five patients).

Results: After a mean follow-up of 28 months (range 12-53 months), the average knee score increased overall from a mean of 33 points (range 12-63) to 78 points (range 63-90). The average functional score improved from a mean of 32 points (range 10-65) to 72 points (range 40-90). The postoperative mechanical axis ranged between 3° of varus and 3° of valgus. There was an implant revision in one patient who had a traumatic rupture of medial collateral ligament, which occurred 27 months after the index procedure.

Conclusions: Based on our results we think that the navigation-assisted technique provides an alternative approach to the traditional instrumentation for treating these difficult patients in an effective and less invasive manner.

Fig. 1

A 77-year-old woman with 24° varus femoral deformity secondary to a supracondylar osteotomy with a history of poliomyelitis involving the lower limbs. a A knee prosthesis had been implanted maintaining an acceptable mechanical axis. b Although there was a co-existent 15° femoral recurvatum deformity, a rotating hinged prosthesis was implanted obtaining good component positioning

Fig. 2

Sequelae of sovracondylar fracture with hardware positioned very far from the joint line (33 mm) and with 10° valgus deviation of the knee (a). Computer-assisted surgery allowed good component positioning with correction of mechanical axis (b)

Fig. 3

A patient with bilateral hip prosthesis and severe valgus of the left knee (a), underwent left knee prosthesis (b). Although good correction of limb axes and correct positioning of the prosthesis, after repetitive trauma, she experienced medial collateral ligament rupture (c)